Which of the following statements is/are true
A) `Na_(2) r_(2), O_(7)` is more soluble in water than `K_(2)CR_(2)O_(7)`
B) `K_(2)Cr_(2)O_(7)` is used as a primary standard in volumetric analysis
C) Both `Na_(2)Cr_(2)O_(7) and K_(2) Cr_(2)O_(7)` are strong oxidizing agents
D) The chromates and dichromates are interconvertible in aqueous solutions 

Options

A. A and B
B. B and C
C. A and D
D. All the above

Answer

To determine which of the statements about the compounds \( Na_2Cr_2O_7 \) and \( K_2Cr_2O_7 \) are true, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** \( Na_2Cr_2O_7 \) is more soluble in water than \( K_2Cr_2O_7 \).

- **Analysis:** Sodium ions (\( Na^+ \)) are smaller than potassium ions (\( K^+ \)). The smaller size of sodium ions allows for better hydration and solvation in water, leading to higher solubility. Therefore, \( Na_2Cr_2O_7 \) is indeed more soluble in water than \( K_2Cr_2O_7 \).

**Conclusion:** Statement A is true.

### Step 2: Analyze Statement B
**Statement B:** \( K_2Cr_2O_7 \) is used as a primary standard in volumetric analysis.

- **Analysis:** Potassium dichromate (\( K_2Cr_2O_7 \)) is widely used as a primary standard due to its stability and known concentration. It can be accurately weighed and used to prepare standard solutions for titrations.

**Conclusion:** Statement B is true.

### Step 3: Analyze Statement C
**Statement C:** Both \( Na_2Cr_2O_7 \) and \( K_2Cr_2O_7 \) are strong oxidizing agents.

- **Analysis:** Both sodium dichromate and potassium dichromate contain the dichromate ion (\( Cr_2O_7^{2-} \)), which is known for its strong oxidizing properties. Therefore, both compounds act as strong oxidizing agents.

**Conclusion:** Statement C is true.

### Step 4: Analyze Statement D
**Statement D:** The chromates and dichromates are interconvertible in aqueous solutions.

- **Analysis:** In aqueous solutions, chromate ions (\( CrO_4^{2-} \)) and dichromate ions can interconvert depending on the pH of the solution. In acidic conditions, dichromate is favored, while in basic conditions, chromate is favored.

**Conclusion:** Statement D is true.

### Final Conclusion
All statements A, B, C, and D are true.

### Summary of True Statements:
- A) True
- B) True
- C) True
- D) True

Thus, the correct answer is that all the statements are true.

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